Tetraazadodecane based chelating agents for separation of rare earth elements and method therefor

Abstract

The present invention related to the use of compounds of general formula (I) for separations of rare earth elements (lanthanides) by precipitation, wherein R is selected from the group consisting of H; —CH2COOH; R 2 , R 3 , R 4 , R 5 and R 6 areindependently selected from the group consisting of H; OH; —NO2; —COOH; phenyl; and/or R 2 and R 3 or R 3 and R 4 or R 4 and R 5 or R 5 and R 6 The invention further relates to a method of separation of rare earth elements by precipitation. together with two neighbouring carbon atoms of the aromatic ring form a six-membered aromatic ring.

1 . A compound of general formula (I) 
       
         
           
           
               
               
           
         
         for separation of rare earth elements by precipitation, 
         wherein 
         R 1  is selected from the group consisting of H; —CH 2 COOH; 
         R 2 , R 3 , R 4 , R 5  and R 6  are independently selected from the group consisting of H; OH; —NO2; —COOH; phenyl; 
         and/or R 2  and R 3  together with two neighbouring carbon atoms of the aromatic ring form a sixmembered aromatic ring; 
         and/or R 3  and R 4  together with two neighbouring carbon atoms of the aromatic ring form a sixmembered aromatic ring; 
         and/or R 4  and R 5  together with two neighbouring carbon atoms of the aromatic ring form a sixmembered aromatic ring; 
         and/or R 5  and R 6  together with two neighbouring carbon atoms of the aromatic ring form a six-membered aromatic ring. 
       
     
     
         2 . The compound according to  claim 1 , wherein at most two of the substituents R 2 , R 3 , R 4 , R 5  and R 6  are other than H. 
     
     
         3 . The compound according to  claim 1 , wherein one of the substituents R 2 , R 3 , R 4 , R 5  and R 6  is other than H. 
     
     
         4 . The compound according to  claim 1 , wherein R 2  and R 6  are independently H or OH. 
     
     
         5 . The compound according to  claim 1 , wherein R 3  and R 4  together with two neighbouring carbon atoms of the aromatic ring form a six-membered aromatic ring and at the same time R 2 , R 5  and R 6  are H. 
     
     
         6 . The compound according to  claim 1 , wherein R 2 , R 3 , R 4 , R 5  and R 6  are H. 
     
     
         7 . The compound according to  claim 1 , wherein the group 
       
         
           
           
               
               
           
         
       
       of the general formula (I) is selected from the group comprising naphtalen-1 -ylmethyl, naphtalen-2-ylmethyl and benzyl. 
     
     
         8 . The compound according to  claim 1 , wherein R 2 , R 3 , R 5  and R 6  are H, and R 4  is phenyl, H or COOH. 
     
     
         9 . The compound according to  claim 1 , wherein the compound of general formula (I) is selected from the group consisting of:
 2,2′,2″-(10-benzyl- 1 ,4,7, 10-tetraazacyclododecane- 1 ,4,7 -triyl)triacetic acid;   2,2′-(4-(2-hydroxy-5-nitrobenzyl)- 1 ,4,7, 10-tetraazacyclododecane- 1 ,7-diyl)diacetic acid;   2,2′-(4-(4-carboxybenzyl)-1,4,7,10-tetraazacyklododekane-1,7-diyl)diacetic acid;   2,2′,2″-(10-(naphthalene-2-ylmethyl)-1,4,7,10-tetraazacyklododekane-1,4,7-triyl)triacetic acid;   2,2′,2″-(10-(naphthalene-1 -ylmethyl)- 1 ,4,7, 10-tetraazacyklododekane- 1 ,4,7-triyl)triacetic acid;   2,2′,2″-(10-([1,r-biphenyl]-4-ylmethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetic acid.   
     
     
         10 . A method of separation of rare earth elements by precipitation, comprising the following steps:
 o) Providing an aqueous solution of ions of at least two different rare earth elements (M 3+ ) to be separated, and an aqueous solution of the compound of general formula (I) defined in any one of the preceding claims, wherein the solvent is selected from the group comprising water, buffer and/or mixture of water and organic solvent miscible with water, wherein the water content is at least 50 vol. %;   a) Reaction of the aqueous solution of ions of at least two different rare earth elements (M 3+ ) to be separated with the aqueous solution of the compound of general formula (I) defined in  claim 1 , at pH in the range of from 5 to 9, to form at least one complex of the M 3+  ion with the compound of general formula (I) in the form of a precipitate or a crystalline phase;   b) Mechanical separation of the precipitate or of the crystalline phase from the reaction mixture;   c) Optionally, re-dissolving of the precipitate or of the crystalline phase from step b) in water, buffer, a mixture of water and organic solvent, which is miscible with water, or in aqueous solution of inorganic or organic acid;   d) Optionally, pH adjustment of the solution from step c) to the pH value in the range of from 5 to 9, and repeating of steps a), b) and optionally c).   
     
     
         11 . The method according to  claim 10 , wherein the compound of the general formula (I) is separated from the reaction mixture after dissolving the precipitate or crystalline phase in step c), preferably using solid phase extraction or chromatography or sorption on activated carbon. 
     
     
         12 . The method according to  claim 10 , wherein the molar ratio between the sum of rare earth metal ions M 3+  and the compound of the general formula (I) is in the range of from 1:0.5 to 1:100. 
     
     
         13 . The method according to  claim 10 , wherein the ions of at least two different rare earth elements (M 3+ ) in the reaction mixture in step a) are in the form of their water-soluble salts with inorganic or organic acids, preferably selected from the group comprising chloride, bromide, sulfate, nitrate, perchlorate, methansulfonate, trifluoromethansulfonate, formate, acetate, lactate, malate, citrate, 2-hydroxy isobutyrate, mandelate, diglycolate and/or tartrate. 
     
     
         14 . The method according to  claim 10 , wherein at least one additive is added into the reaction mixture in step a), wherein the additive is selected from the group comprising carboxylic acids comprising from 1 to 11 carbon atoms, phosphinic acids comprising from 1 to 10 carbon atoms, phosphonic acids comprising from 1 to carbon atoms, trifluoroacetic acid, 3-chlorobenzoic acid, chloride; dipicolinic acid, fluoride, glycine, glycolate, alpha-hydroxyisobutyric acid, lactate, nitrate, phenylboronic acid, picolinic acid, pyridine, mandelic acid, salicylic acid, sulfate, thiocyanate, tributyl phosphate, dimethylsulfoxide, /, /-dimethylformamide, N,N-dimethylacetamide ;
 preferably the additive is selected from the group comprising acetate, trifluoroacetic acid, benzoic acid, 3 -chlorobenzoic acid, 2-methylbenzoic acid, 3 -methylbenzoic acid, 4-methylbenzoic acid, chloride, citrate, dipicolinic acid, fluoride, formate, glycine, glycolate, oc-HIBA (alphahydroxyisobutyric acid), lactate, nitrate, phenylboronic acid, picolinic acid, pyridine, mandelic acid, salicylic acid, sulfate, thiocyanate, tributyl phosphate, dimethylsulfoxide, /, /-dimethylformamide, N, /V-dimethy lacetamide .   
     
     
         15 . The method according to  claim 14 , wherein the molar ratio between the sum of rare earth metal ions and the additive in the reaction mixture of step a) is in the range of from 1:0.1 to 1:100. 
     
     
         16 . The method according to  claim 10 , characterized in that it further comprises a step e) in which the reaction mixture from step b), after mechanical separation of the precipitate or of the crystalline phase, is subjected to evaporation and/or ultrafiltration and/or ion-exchange chromatography, resulting in precipitation or crystallization of at least one complex of the M 3+  ion with the compound of general formula (I).